1. Field of the Invention
The present invention relates to a removable coupling device. More particularly, it relates to removable coupling devices in which a shaft is insertable into a boss member having radially movable locking elements to lock the shaft.
One type of removable coupling device comprises a boss member having a hole axially extending inwards and apertures radially extending to open in the hole. A shaft having a set groove circumferentially extending in an outer surface thereof is fitted into the hole of the boss member. Locking elements are radially movably disposed within the respective apertures of the boss member such that the locking elements can extend partly inwards from the apertures so as to engage with the set groove of the shaft to thereby prevent the shaft from escaping from the hole of the boss member. A set ring is axially movably disposed on the boss member to keep the locking elements at either a locking position where their locking elements are engaged with the set groove of the shaft or at a connectable and disconnectable position where the locking elements are disengaged from the set groove so as to be movable radially outwards.
Coupling devices of this type have advantages in that, when the shaft is inserted into the boss member, the shaft can be inserted without holding the set ring and can be automatically kept at the lock position if the set ring on the boss member is axially slidably moved. An additional advantage is that, when the shaft is removed from the boss member, the shaft can be removed form the boss member without holding the set ring if the set ring is axially slidably moved. Accordingly, for example, in the case where the coupling device of this type is used to drive agricultural machinery to be connected to a tractor through a motive power transmission shaft, the device is useful for the connection between a boss member having a universal joint yoke and an output shaft of the tractor or the connection between the boss member and an input shaft of the agricultural machinery. On the other hand, in the case where a tractor merely pulls a car or the like, a shaft of the tractor can be removably connected to a shaft of the car by the device. Furthermore, the device can be used as a coupling device for connecting and disconnecting pipes such as fire hoses or the like or can be used as as coupling device for establishing scaffolding for building construction.
Although shafts for transmitting rotational motive power are used in various kinds of machines, the shafts are difficult to handle in connecting and disconnecting operations and often cause danger because the joint portion thereof is generally disposed at a narrow portion and/or because covers are provided to prevent stain. In order to solve such problems, various kinds of devices for safely, securely and speedily performing the connection of the shafts have been proposed. Among those proposals, such a coupling device as described above in the head portion, in which the connection and disconnection of the shaft can be easily made by axially moving the set ring when the shaft is inserted into or removed from the boss member, has been proposed in the specification and drawings initially appended to the request of an application of each of Japanese Patent Unexamined Publication Nos. 41017/1986, 52420/1986 and 84410/1986 and Japanese Patent Application No. 118949/1985 (corresponding to U.S. Patent Application Ser. No. 779,268, filed Sept. 23, 1985).
However, those proposed devices are disadvantageous in that many parts are required, the structure is complex, a long time is required for assembling the coupling device, and high cost is required for manufacturing the coupling device.
Reference is also made to a removable coupling device having similarities to these described in Japanese Patent Application 260058/85.